Glass-Ceramic Composite Encapsulation Material
A glass-ceramic composite encapsulation material composed of glass matrix materials of SiO2, Al2O3, BaO and B2O3, and at least one glass filler selected from the group consisting of kaliophilite (KAlSiO4), leucite (KAlSi2O6), magnesium oxide (MgO). The glass-ceramic composite encapsulation material according to the invention comprises a high temperature type glass matrix (softening point: 750-850° C.) and a intermediate temperature type glass matrix (softening point: 650-750° C.), and glass filler mixed therein, wherein said glass filler in the high temperature type glass matrix comprises 5% to 20% by volume of the total volume of said glass matrix and glass filler, and the glass filler in the intermediate temperature type glass matrix comprises 0% to 40% by volume of the total volume of said glass matrix and glass filler, and wherein said glass filler has an effect of adjusting the expansion coefficient.
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1. Field of the Invention
The invention relates to a glass-ceramic composite encapsulation material, and in particular, to a glass-ceramic composite encapsulation material characterized in that it is prepared by incorporating at least one glass filler selected from the group of KAlSiO4, KAlSi2O6, and MgO in a Ba—B—Si—Al glass matrix, and is applicable to solid oxide fuel cell technology.
2. Description of the Prior Art
Among various fuel cell technologies, solid oxide fuel cells (SOFC) possess advantages such as high conversion efficiency, a wide selection of fuel sources, and lower material cost. However, its working temperature is very high (about 700° C.-1000° C.), and as a result, in the manufacture of a plate SOFC, a high temperature encapsulation technique is required to fill up interstices between plates with encapsulation materials so as to insulate fuel gas from oxygen. Therefore gas tight layers and joints are necessary between materials. Since the entire SOFC elements is operated under high temperature, under normal starting and stopping conditions, materials may experience temperature cycles ranging from normal and high. As a result, matching the thermal expansion coefficients of the various elements is important. Consequently, some types of encapsulation materials play a role as a buffer to reduce damage to the elements caused by the stress generated from heat expansion and cold shrinkage.
When a glass material is used to seal a solid oxide fuel cell, the mechanism for how to add oxides to lower the softening point of the glass to match the thermal expansion coefficients of the other materials to be encapsulated has not been sufficiently tested. The difference in the expansion coefficient of encapsulation glass and materials to be encapsulated results cracks to form in the barrier. In addition, the use of alumina, boron oxide, barium oxide, silica, kaliophilite (KAlSiO4), leucite (KAlSi2O6) and magnesium oxide (MgO) in the material have not been adequately tested.
In view of this, the above-described conventional art has many disadvantages and requires a solution.
In light of various disadvantages derived from the above-described methods, the inventor had devoted to improve and innovate, and finally, after studying intensively for many years, successfully developed a glass-ceramic composite encapsulation material according to the invention herein.
SUMMARY OF THE INVENTIONOne object of the invention is to provide a glass-ceramic composite encapsulation material characterized in that it can modify and lower the softening point of a glass material, extend the range of operating temperature, and adjust the effect of its expansion coefficient. In addition, one object of this invention is to achieve a glass encapsulation material composite that has a low softening point, good air tightness, a controllable thermal expansion coefficient and compression sealing property.
Another object of the invention is to provide glass-ceramic composite encapsulation material characterized in that it can control the flow range of a glass, prevent it from permeating into other materials due to excess flow, as well being able to accelerate the crystallization of glass, thereby facilitating the conversion an originally unstable glass to a glass-ceramic of in a shorter time period, whereby a the stable glass-ceramic will cause less erosion to nearby elements.
A glass-ceramic composite encapsulation material that can achieve the above-described objects of the invention comprises: glass matrix materials of SiO2, Al2O3, BaO and B2O3; and at least one type of glass filler selected from the group consisting of KAlSiO4, KAlSi2O6, and MgO. The inventive glass-ceramic composite encapsulation material includes high temperature type glass matrix and intermediate temperature type glass matrix mixed with a glass filler, wherein the glass filler in the high temperature type glass matrix comprises 5% to 20% by volume of the total volume of said glass matrix and glass filler, while the glass filler in the intermediate temperature type glass matrix comprises 0% to 40% by volume of the total volume of said glass matrix and glass filler; thereby, the glass-ceramic encapsulation material for a solid oxide fuel cell can readily adjust the softening point and the thermal expansion coefficient.
These features and advantages of the present invention will be fully understood and appreciated from the following detailed description of the accompanying drawings, wherein:
The sum of the mole proportion of the ingredients SiO2 and Al2O3 composite in the high temperature type glass matrix comprises 50% to 72% of the total mole number of glass matrix, Al2O3 comprises 3% to 15% of the total mole number of the glass matrix, BaO is a modifier for adjusting the softening point of the glass comprising 10% to 30% of the total mole number of glass matrix; B2O3 is a modifier for adjusting the softening point of glass comprising 15% to 35% of the total mole number of glass matrix, and at least one filler comprising 20% to 40% by volume of the total volume of the glass is selected from the group consisting of KAlSiO4, KAlSi2O6, and MgO and is incorporated in the glass matrix to form a glass-ceramic composite encapsulation material with an adjustable expansion coefficient.
The sum of the mole proportions of the ingredients SiO2 and Al2O3 composite in the intermediate temperature type glass matrix comprises 20% to 50% of the total mole number of the glass matrix, BaO is a modifier for adjusting the softening point of the glass comprising 20% to 50% of the total mole number of the glass matrix, B2O3 is a modifier for adjusting the softening point of glass comprising 30% to 60% of the total mole number of the glass matrix, and at least one filler comprising 20% to 40% by volume of the total volume of the glass is selected from the group consisting of KAlSiO4, KAlSi2O6, and MgO and is incorporated in the glass matrix to form a glass-ceramic composite encapsulation material with an adjustable expansion coefficient.
An encapsulation paste comprising a binder that is prepared by the following steps: using polyvinyl acetate (PVAC) as a base; weighing main ingredients of said glass to be formulated; wetting the mixture of main ingredients with alcohol at the proper weight ratio (mix:alcohol=10:4), mixing homogeneously; adding the thus-obtained mixture in said PVAC at a weight ratio of mix:PVAC=10:1; stirring this mixture continuously to increase the viscosity thereof until the resulted slurry becoming a paste; and packing the thus-obtained paste in a syringe that is used to inject at a position to be encapsulated.
The ratio of SiO2/B2O3 is an important reference factor in the reduction of the softening point given the reason that B2O3 is itself a glass structure forming agent and the boron glass itself has a low softening point (about 450-600° C.). Therefore by increasing the ratio of B2O3 viscosity can be reduced. The glass structure modifier of this system is BaO, and since Ba has a high atomic mass, it possesses a strong potential to disrupt the glass matrix structure, and consequently, the addition of BaO in the glass system can adjust the softening point.
The effect of change in ratios of B2O3 and BaO on the property of glass has been investigated in this invention. For the convenience of expressing data, among all the four ingredients, the mole proportions of Al2O3 and SiO2 are summed together, since Al2O3 acts as a glass structure intermediate agent and is present in the formulation at a constant proportion. As shown in
Referring to
Referring to
The glass-ceramic composite encapsulation material provided according to the invention has the following advantages over other conventional techniques:
- 1. The inventive glass-ceramic composite encapsulation material can adjust the expansion coefficient and softening point as required in a certain range, and thus can produce an encapsulation material suitable for SOFC by means of an identical process under this mode.
- 2. The inventive glass-ceramic composite encapsulation material comprises a glass matrix that is formed with four kinds of low cost ingredient materials at various formulation ratios, and achieves the additional objectives of lowering the softening point of glass encapsulation material, having a good air tightness and a controllable thermal expansion coefficient, as well as compression sealing. Furthermore, products derived from the inventive material can sufficiently fulfil the encapsulation requirement of the present solid oxide fuel cell.
The foregoing detailed description gives a concrete illustration of a practical embodiment of the invention, however, this is not intended to limit the patent right scope of the invention. Equivalent modifications or variations not deviating from the art or spirit of the invention are intended to fall within the patent scope of the invention.
Many changes and modifications in the above-described embodiment of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims.
Claims
1. A glass-ceramic composite encapsulation material, wherein said glass matrix is based on materials selected from the group consisting of SiO2, Al2O3, BaO and B2O3, and is to be mixed with glass filler to form a glass-ceramic composite.
2. A glass-ceramic composite encapsulation material as in claim 1, wherein said glass filler is used to adjust encapsulation expansion coefficient, and to form a glass-ceramic composite encapsulation material.
3. A glass-ceramic composite encapsulation material as in claim 1, wherein said glass filler is one selected from the group consisting of kaliophilite, leucite and magnesium oxide.
4. A glass-ceramic composite encapsulation material as in claim 1, wherein the material of said glass matrix is one selected from the group consisting of a high temperature type glass matrix mixed with glass filler and an intermediate temperature type glass matrix mixed with glass filler.
5. A glass-ceramic composite encapsulation material as in claim 4, wherein said high temperature type glass matrix has a softening point of 750-850° C.
6. A glass-ceramic composite encapsulation material as in claim 4, wherein said intermediate temperature type glass matrix has a softening point of 650-750° C.
7. A glass-ceramic composite encapsulation material as in claim 4, wherein the sum of mole ratios of SiO2 and Al2O3 composite of said high temperature type glass matrix comprises 50% to 72% of the total mole number of said glass matrix.
8. A glass-ceramic composite encapsulation material as in claim 4, wherein Al2O3 in said high temperature type glass matrix comprises 3% to 15% of the total mole number of said glass matrix.
9. A glass-ceramic composite encapsulation material as in claim 4, wherein BaO in said high temperature type glass matrix is a modifier for adjusting the softening point of glass, and BaO comprises 10% to 30% of the total mole number of said glass matrix.
10. A glass-ceramic composite encapsulation material as in claim 4, wherein B2O3 in said high temperature type glass matrix is a modifier for adjusting the softening point of glass, and B2O3 comprises 15% to 35% of the total mole number of said glass matrix.
11. A glass-ceramic composite encapsulation material as in claim 4, wherein said glass filler in said high temperature type glass matrix comprises 5% to 20% by volume of the total volume of said glass matrix and glass filler.
12. A glass-ceramic composite encapsulation material as in claim 4, wherein the sum of mole ratios of SiO2 and Al2O3 composite in said intermediate temperature type glass matrix comprises 20% to 50% of the total mole number of said glass matrix.
13. A glass-ceramic composite encapsulation material as in claim 4, wherein Al2O3 in said intermediate temperature type glass matrix comprises 3% to 15% of the total mole number of said glass matrix.
14. A glass-ceramic composite encapsulation material as in claim 4, wherein BaO in said intermediate temperature type glass matrix is a modifier for adjusting the softening point of glass, and BaO comprises 20% to 50% of the total mole number of said glass matrix.
15. A glass-ceramic composite encapsulation material as in claim 4, wherein B2O3 in said intermediate temperature type glass matrix is a modifier for adjusting the softening point of glass, and B2O3 comprises 30% to 60% of the total mole number of said glass matrix.
16. A glass-ceramic composite encapsulation material as in claim 4, wherein said glass filler in said intermediate temperature type glass matrix comprises 0% to 40% by volume of the total volume of said glass matrix and glass filler.
Type: Application
Filed: Apr 22, 2009
Publication Date: Oct 28, 2010
Patent Grant number: 8158261
Applicant: National Taipei University Technology (Taipei City)
Inventors: Sea-Fue Wang (Taipei City), Yun-Ruey Wang (Taipei City), Ching-Chin Chuang (Taipei City), Chun-Ting Yeh (Taipei City)
Application Number: 12/428,018
International Classification: C03C 14/00 (20060101);